Single wave transmitting system



Dec. 8, 1936. w. M. HAHNEMANN SINGLE WAVE TRANSMITTING SYSTEM Filed Aug. l5, 1933 Fragua/191 /l/algaln Fr Mechanica dscEZZaa/v N Cantrol t Trans/nite Freq/amy Mahi/plier' Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE SINGLE WAVE TRANSMITTING SYSTEM Application August 15,

1933, Serial No. 685,267

In Germany April 5, 1932 6 Claims.

This invention relates to arrangements for actuating high frequency transmitters which operate with waves of the same length, such as in the so-called common or single wave broadcasting.

Two different general types of system have been developed for this form of broadcasting. In one system a control frequency or fundamental frequency is transmitted from a central station to the several transmitters. In the other system entirely local synchronization is `performed at the Various transmitters by means of quartz crystals or tuning forks. The first system, in which a control or fundamental frequency is conveyed over cable lines to the individual transmitters, permits better synchronization but the characteristics of the cables have rendered it necessary to employ a control frequency of a relatively low period and to step this up by several stages of frequency multiplication. Moreover, filters must be provided at the individual transmitting stations to prevent the secondary or harmonic frequencies produced by a frequency multiplier from being multiplied in the subsequent of secondary waves formed. In the United States Patent No. 1,920,194 to Gerth there is described such a system in which a plurality of cascadeconnected devices are provided each consisting of an amplifier, a frequency multiplying device and a filter or disturbance-removing device arranged' in cascade. This arrangement, however, is somewhat expensive to install and it is an object of the present invention to provide a more economical system.

In accordance with the present invention the control or fundamental frequency is first multiplied at the transmitting stations and is then caused to act 0n a mechanical oscillation device of very low attenuation which only passes the desired multiplied frequency. The purified multiplied frequency is then subjected to another stage of frequency multiplication and, subsequently, radiated, or it is employed'to regulate the frequency generated by the transmitter.

The invention will be understood from the following description and be particularly pointed out in the appended claims, reference being had to the accompanying drawing in which Fig. l is a wiring diagram, Fig. 2 a diagrammatic detail View of a device shown also in Fig. 1. Fig. 3 is a diagrammatic detail view representing a slight modification of the device illustrated in Fig. 2. Fig. 4 illustrates another form of memultiplying stage and, thus, an undesired band chanical oscillator, which may be advantageously employed.

In Fig. 1, Z denotes a central station that serves to produce the control frequency for a number of transmitting stations S connected to this sta- 5 tion by cable lines A. Only two transmitting stations are shown for simplicity.

Each transmitting station S is provided with a frequency multiplier F, a mechanical oscillatory device G attenuated to a very low degree, a second l0 multiplier N, and a disturbance remover or lter St.

The multipliers F and N preferably consist of well-known combinations of electron tubes. The device St and an arrangement S constitute the customary end portion of an arrangement for single wave transmission.

The action is as follows.

The control frequency produced in the station Z be assumed to be 2000 cycles per second and to be multiplied by the multipliers F to 400,000 cycles per second. The devices G act to purify this increased frequency of harmonics and to transfer it to the multipliers N by each of which it is multiplied to say 1,600,000 cycles per second.

The simple multipliers` F, N and the device G thus take the place of the two stages required in prior arrangements of said U. S. Patent No. 1,902,194 which are each comprised of an ampliner, a multiplier, and a filter or disturbance removing device. The novel arrangement is therefore much more simple than the prior ones while being of at least equal efficiency.

The devices G may operate by means of steel bars caused to perform longitudinal oscillations. Such bars may, for instance, be subjected to magnetostriction. Quartz pieces are likewise adapted for this purpose. While on the one hand the device G must be attenuated to a very lo-w degree, it must on the other hand be such that there is no direct coupling between the exciting and the excited circuits. In the case of a steel bar, for example, the arrangement must be such that the input and output circuits are not coupled to each other byV this bar, but that its movements shall excite the output circuit only.

The device G shown in Fig. 2 has a quartz crystal Q as the means to which the said very low attenuation is due. El denotes a pair of electrodes, E2 a `second pair thereof. The crystal Q is excited at one end by the electrodes El. The piezo-electric tensions are conducted away by the electrodes E2. These pairs of electrodes are spaced at the largestpossible distance apart to prevent direct capacitive couplings from arising between them.

As will be seen from Fig. 3, the pairs of the electrodes El, E2 may be offset at right angles with respect to each other. The quartz crystal Q is so chosen in this case as to be excited in accordance with the optical axis best adapted for the purpose, the electrodes E2 being applied to the other faces of the crystal Q.

Instead of the quartz crystal G of Fig. 2, another form of mechanical oscillator GS, according to Fig. 4, may be employed. This mechanical oscillator GS comprises a steel bar BS provided with coils Wl, W2 and W2 which may be respectively connected in the circuit in Fig. 2 in the same manner as the electrodes El, E2 and E2. This steel bar with its windings comprises a device operated by magneto striction.

The device G may be so arranged that it is controlled continuously over the multiplier F by the frequency arriving over the line A, as is shown in connection with each of the two upper transmitters in Fig. l. It is, however, also possible to provide additional means whereby the device G is simultaneously self-excited, as is illustrated in Fig. 2. A coil LI is arranged in the input circuit of the crystal Q and a coil L2 is connected in the output circuit. The coils LI and L2 are coupled together so that a back-coupling exists and self-excitation of the system is secured. By throwing the switch U to connect the line A to the frequency multiplier F, control of the device G may be simultaneously effected from the central station. On the other hand, if the line A is disconnected from the multiplier F by opening the switch U, no control is exercised from the central station. Such an arrangement has the great advantage that if the transmission channel is disconnected from the central station, for example, on account of a line breakdown, the transmitter is maintained on its wave by self-excitation and remains operable. If this occurs certain differences in the frequencies of the individual transmitters may arise whereby the field of disturbance between them is increased; but such disturbances are preferable to the collapse of the entire transmission system and, as the disturbed area is usually so located that it falls in a sparsely populated district, such a breakdown does not make itself very noticeable in the general transmission service.

As an alternative to the back-coupling arrangement shown in Fig. 2, additional electrodes may be employed with the quartz crystal to effect selfexcitation.

According to a further modification the frequency from the device G is not used to excite directly the transmitters S, but such frequency may be employed to regulate the frequency of the transmitters. Such a method has Various advantages which will be explained hereafter.

In single wave broadcasting, under some circumstances, it is possible by the use of local quartz control devices to construct the transmitters so that they may remain constant in frequency for a relatively long time, and the fluctuations of the carrier frequencies of the individual transmitters are so small that over long periods the disturbances are negligible. With such transmitters, however, after a certain time the deviation of the individual carrier waves becomes excessive and disturbances occur which are not permissible. According to a further modification the control from the central station of the frequencies of the individual single Wave transmitters may be effected at predetermined time intervals. With this arrangement the great advantage is obtained that the lines employed for the control of the transmitters are only used for a short time and, during the rest of the time, may be employed as transmission or signalling lines or for any other purpose. Thus, for example, with suitable construction of the individual transmitters it is necessary to provide supervision and adjustment of the single wave transmitter from the central station only once a day, for example in the morning, and to employ the line during the remaining time for telephone connections for the transmission of the modulation frequencies. In Fig. 2, for example, the line is conveyed over the switch U and may be connected alternatively to the device G or to the other line employed for other purposes.

The following is a description of a preferred arrangement and method of operationz--At the central station Z and at each of the individual transmitters S there are provided frequency generators which are controlled by quartz crystals. Fig. 1 shows such an arrangement in connection with the third transmitter, G being the quartz crystal oscillator at the transmitter. The frequency arriving from the central station Z over the frequency multiplier F and the oscillation structure G may be compared with the frequency generated by the oscillator G' of the transmitter. If it is now found that a diierence exists between these two frequencies, a new adjustment of the transmitter may be made. In this way it is possible to indicate immediately phase variations of the transmitters, since the frequency multiplying devices operate with relatively high periodicities. Simple arrangements may be provided for correcting such variations. A suitable device is also shown in Fig. 1. The frequency conveyed from the central station Z over the frequency multiplier F and the oscillation structure G is conveyed by means of the switch U to a phase meter P, to which at the same time is also conveyed the frequency G' generated by the oscillation generator of the transmitter itself. According to whether the phase between the two frequencies varies to one side or the other, a pointer deection is obtained to the right or the left. If the deflection reaches a magnitude at which the phase difference between the two frequencies is excessively high, then a contact is closed by the pointer which closes the circuit for a motor M. The motor M in turn rotates the plate of a rotary condenser located in a tuning circuit of the control transmitter S and in this way varies the frequency according to the setting of the phase meter. According to the deflection of the instrument the motor makes a rotation to the right or to the left. As this phase compensation only need be performed at relatively long time intervals, there may be provided before the frequency multiplier F a further switch (not shown in the drawing) which renders it possible to disconnect the line coming from Z from the frequency multiplier F and to employ it for other purposes. In the example shown in Fig. l the two frequencies which are conveyed to the phase meter P from the oscillation structure G and the oscillation generator G are of the order of 400,000 cycles. It is, of course, also possible to employ any other suitable method of phase regulation.

Changes may be made within the scope indicated by the appended claims, without departing from the spirit of the invention.

What is claimed is:

1. A single wave radio transmitting system in which a control or fundamental frequency is transmitted over metallic wires from a central station to individual transmitting stations and comprising at each transmitting station a two stage frequency multiplying equipment connected in cascade, the first stage comprising a frequency multiplier having a high multiplication constant and a mechanical oscillation structure of low attenuation and high selectivity for passing only the desiredmultiplied frequency with means for delivering the multiplied frequencies from the multiplier to said mechanical oscillation structure, and said second stage comprising a frequency multiplier having a low multiplication constant followed by a filter for suppressing substantially all frequencies except a desired multiple of the multiplied frequency, and means for delivering to the second stage multiplier the desired multiplied frequency passed by said mechanical oscillation structure.

2. A single wave radio transmitting system in which a control or fundamental frequency is transmitted over metallic wires from a central station to individual transmitting stations and comprising at each transmitting station a two stage frequency multiplying equipment connected in cascade, the rst stage comprising a frequency multiplier having a high multiplication constant and a mechanical oscillation structure in the form of a quartz crystal of low attenuation and high selectivity for passing only the desired multiplied frequency with means for delivering the multiplied frequencies from the multiplier to said oscillation structure, and said second stage comprising a frequency multiplier having a low multiplication constant followed by a filter for suppressing substantially all frequencies except a desired multiple of the multiplied frequency, and means for delivering to the second stage multiplier the desired multiplied frequency passed by said oscillation structure.

3. A single wave radio transmitting system in which a control or fundamental frequency is transmitted `over metallic wires from a central station to individual transmitting stations and comprising at each transmitting station a twostage frequency multiplying equipment connected in cascade, the first stage comprising a frequency multiplier having a high multiplication constant and a mechanical oscillation structure of low attenuation and high selectivity for passing only the desired multiplied frequency with means for delivering the multiplied frequencies from the multiplier to said mechanical oscillation structure, and said second stage comprising a frequency multiplier having a low multiplication constant followed by a lter for suppressing substantially all frequencies except a desired multiple of the multiplied frequency, and means for delivering to the second stage multiplier the desired multiplied frequency passed by said mechanical oscillation structure, said mechanical oscillation structure comprising a quartz crystal provided with two sets of electrodes one set being located at one end of the crystal and the other set at the other end thereof, one set of the electrodes serving for exciting the crystal and the other being excited thereby.

4. A single wave radio transmitting system in which a control or fundamental frequency is transmitted over metallic wires from a central station to the individual transmitting stations and comprising at each transmitting station a frequency multiplier, a mechanical oscillation structure of very low attenuation for passing only the desired multiplied frequency, means for first impressing said control or fundamental frequency upon said frequency multiplier, means for then conveying from said multiplier the multiplied frequency thereby obtained to said mechanical oscillation structure, wherein said mechanical oscillation structure comprises a quartz crystal provided with two sets of electrodes one set being located at one end of the crystal and the other set at the other end thereof, one set of the electrodes serving for exciting the crystal and the other being excited thereby, and wherein the two sets of electrodes are offset at right angles with respect to each other.

5. A single wave radio transmitting system in which a control or fundamental frequency is transmitted over metallic wires from a central station to individual transmitting stations and comprising at each transmitting station a two stage frequency multiplying equipment connected in cascade, the rst stage comprising a frequency multiplier having a high multiplication constant and a mechanical oscillation structure of low attenuation and high selectivity for passing only the desired multiplied frequency with means for delivering the multiplied frequencies from the multiplier to said mechanical oscillation structure, means for causing said mechanical oscillation structure to produce oscillations, and said second stage comprising a frequency multiplier having a low multiplication constant followed by a fllter for suppressing substantially all frequencies except a desired multiple of the multiplied frequency, and means for delivering to the second stage multiplier the desired multiplied frequency passed by said mechanical oscillation structure.

6. A single wave radio. transmitting system in which a control or fundamental frequency is transmitted over metallic wires from a central station to individual transmitting stations and comprising at each transmitting station a two stage frequency multiplying equipment connected in cascade, the rst stage comprising a frequency multiplier having a high multiplication constant and a mechanical oscillation structure of low attenuation and high selectivity for passing only the desired multiplied frequency with means for delivering the multiplied frequencies from the multiplier to said mechanical oscillation structure, and said second stage comprising a frequency multiplier having a low multiplication constant followed by a filter for suppressing substantially all frequencies except a desired multiple of the multiplied frequency, and means for delivering to the second stage multiplier the desired multiplied frequency passed by said mechanical oscillation structure, a transmitter at each transmitting station, and means for regulating the frequency of the transmitter by the puried multiplied frequency obtained from the mechanical Oscillation structure.

WALTER M. HAI-INEMANN. 

